An important challenge in oil and gas well production is accessing hydrocarbons that are locked in formation and not readily flowing. In such cases, treatment or stimulation of the formation is necessary to fracture the formation and provide passage of hydrocarbons to the wellbore, from where they can be brought to the surface and produced.
Fracturing of formations via horizontal wellbores traditionally involves pumping a stimulant fluid through either a cased or open hole section of the wellbore and into the formation to fracture the formation and produce hydrocarbons therefrom.
In many cases, multiple sections of the formation are desirably fractured either simultaneously or in stages. Tubular strings for the fracing of multiple stages of a formation typically include one or more fracing tools separated by one or more packers.
In some circumstances frac systems are deployed in cased wellbores, in which case perforations are provided in the casing to allow stimulation fluids to travel through the fracing tool and the perforated casing to stimulate the formation beyond. In other cases, facing is conducted in uncased, open holes. In the case of multistage, open hole fracing it is often a challenge to effectively isolate sections of the formation. This is due to the uneven inner surface of the open wellbore and the difficulty of making sufficient sealing contact between the packing elements of the packers and the surface.
A number of packers are known in the art including swellable that comprise substances which react with hydrocarbons or water in the wellbore and are caused to swell. Swellable packers are dependent on sufficient exposure of the swellable substance to wellbore fluids that trigger swelling. The process of full packing off of the section to be fraced can take days to weeks using such swellable packers. Inflatable packers are also known in the art and are activated by inflation of packing elements with a gas or air.
Hydraulic packers are typically defined as packers in which the packing elements can be activated by hydraulic pressure from wellbore fluids. Hydraulic packers have also been used in some open hole cases, however they typically require multiple packing elements per packer to provide sufficient contact with the open hole inner wellbore surface and to provide proper isolation for multistage packing.
A need therefore exists in the art for packers that are simple in construction, small in size and effective at packing off in open hole wellbores.